1. Field of the Invention
The present invention relates to a display apparatus that displays images by driving light emitting elements arranged by pixels by an electric current. More specifically, the present invention relates to a display apparatus of the so-called active matrix type in which the amount of current that is passed through a light emitting element, such as an organic EL element and the like, is controlled by an insulated gate type field effect transistor that is provided in each pixel circuit. More specifically, the present invention relates to a technology for optimizing the size of the transistor that is formed in each of the pixel circuits, and it also relates to an electronic device into which such a display apparatus is incorporated.
2. Description of Related Art
In image displaying apparatuses, such as liquid crystal displays, for example, numerous liquid crystal pixels are arranged in a matrix, and an image is displayed by controlling the transmission intensity or reflection intensity with respect to the incident light for each pixel in accordance with the image information for the image to be displayed. The same principle applies to an organic EL display that uses organic EL elements for its pixels, but unlike liquid crystal pixels, organic EL elements emit light themselves. As a result, organic EL displays offer such advantages over liquid crystal displays as better visibility of image, faster response speed, not requiring a backlight, and so forth. In addition, the brightness level (scale) of each light emitting element is controllable by way of the value of the current that flows therethrough, and thus organic EL displays differ from liquid crystal displays, which are controlled by voltage, in that they are controlled by current.
With organic EL displays, as with liquid crystal displays, there is the simple matrix method and the active matrix method with respect to their driving methods. While the former has a simple structure, it has a problem in that application to large and high definition displays is difficult. As a result, development of the active matrix method is currently being actively pursued. This method is one in which the current that flows through the light emitting element within each pixel circuit is controlled by an active element (generally, a thin film transistor (TFT)) that is provided within the pixel circuit, and descriptions thereof can be found in the following patent documents.
[Patent Document 1] Japanese Patent Application Publication No. JP 2003-255856
[Patent Document 2] Japanese Patent Application Publication No. JP 2003-271095
[Patent Document 3] Japanese Patent Application Publication No. JP 2004-133240
[Patent Document 4] Japanese Patent Application Publication No. JP 2004-029791
[Patent Document 5] Japanese Patent Application Publication No. JP 2004-093682